An efficient swirl-pipe transition geometry

Swirl flow in pipes provides improved particle distribution and particle impingement conditions at relatively low velocities. Less pumping power is consumed in keeping particles in suspension thereby providing the opportunity to operate at even lower slurry velocities. Wear is reduced as a consequence of the lower velocities. Several years of research into swirl inducing pipes at the University of Nottingham have indicated a lobed geometry of fixed cross-section and constant helix as a near-optimum design. However the sudden cross-sectional change in transferring from circular pipe to swirl pipe, and vice versa, results in high entry and exit pressure losses. Transition ducts immediately prior to, and after the swirl pipe can significantly reduce these losses. They provide a gradual change from circular to lobed geometry and also produce higher swirl intensity at the exit of the swirl pipe. This paper details the design of several different transition geometries and their optimisation using validated Computational Fluid Dynamics (CFD) models.